Synthesis, crystal structure and Hirshfeld surface analysis of 1-[(1-octyl-1H-1,2,3-triazol-4-yl)methyl]-3-phenyl-1,2-dihydroquinoxalin-2(1H)-one

The dihydroquinoxaline unit in the title molecule is not quite planar and the molecule adopts a hairpin conformation due in part to an intramolecular C—H⋯O hydrogen bond. In the crystal, the polar portions of the molecules are associated through C—H⋯O and C—H⋯N hydrogen bonds and C—H⋯π(ring) and C= O⋯π(ring) interactions, forming thick layers parallel to the bc plane and with the n-octyl groups on the outside surfaces.


Figure 1
The title molecule with labeling scheme and 50% probability ellipsoids.
The intramolecular hydrogen bond and C-H� � ��(ring) interaction are shown, respectively, by black and green dashed lines. of the layers involves primarily van der Waals contacts between these groups.2021d).The two with the substituent on the ring nitrogen of the dihydroquinoxaline that includes the 1,2,3-triazol-4-yl ring (ECUCOY and FOFCIQ) adopt comparable hairpin conformations.In the former, this results from an intramolecular �-stacking interaction between the two carbonyl groups, which are nearly antiparallel to each other (centroid-centroid distance = 2.95 A ˚) while in the latter, there is an intramolecular C-H� � �O hydrogen bond analogous to that in the title molecule.A Ushaped conformation is adopted by IDOSUR but there is no intramolecular interaction with the side chain.In all the others, the substituent on the ring nitrogen is in a largely extended conformation.In the examples cited, the dihydroqinoxaline moiety ranges from essentially planar (AZAZEC, ESUKUB, XEXWIJ and YAJGEX) to having a dihedral angle between the mean planes of the constituent rings as large as 4.51 (4) � (MAGBIJ).Additionally, the dihedral angle between the mean plane of the heterocyclic ring in the dihydroquinoxaline and that of the attached phenyl ring varies from 9.05 (7) � in ECUCOY to 43.61 (4) � in RIRBOM with the majority of them having this angle greater than 20 � .

Hirshfeld surface analysis
A Hirshfeld surface analysis was performed with Crystal-Explorer (Spackman et al., 2021) and the interpretation of the several plots obtained is described by Tan et al. (2019).Fig. 6a shows the d norm surface together with four neighboring molecules.Those above and below the surface show the C-H� � �O hydrogen bonds while those on the right show the   C-H� � �N hydrogen bonds, which are also depicted in Fig. 2. Fig. 6b shows the surface calculated over the shape function with one neighboring molecule illustrating the C7 O1� � ��(ring) interaction.Fig. 7a is a 2-D fingerprint plot of all types of intermolecular interactions with the remainder of the sections showing delineation into specific atom-atom contacts.The H� � �H contacts (Fig. 7b) contribute the lion's share, which is not surprising considering the high hydrogen content, particularly in the n-octyl portion.These are followed by N� � �H/H� � �N (Fig. 7c), C� � �H/H� � �C (Fig. 7d) and O� � �H/ H� � �O (Fig. 7e) contacts in order of decreasing percentage contribution.The N� � �H/H� � �N and O� � �H/H� � �O plots show rather sharp spikes as a result of the H� � �O and H� � �N distances having a narrow range of values since they primarily represent the C-H� � �O and C-H� � �N hydrogen bonds.All other contacts contribute considerably less, for example, the O� � �C contacts involving the C7 O1� � ��(ring) interactions contribute only 1.3% of the total.

Special details
Geometry.All esds (except the esd in the dihedral angle between two l.s.planes) are estimated using the full covariance matrix.The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry.An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s.planes.Refinement.Refinement of F 2 against ALL reflections.The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 .The threshold expression of F 2 > 2sigma(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement.R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.H-atoms attached to carbon were placed in calculated positions (C-H = 0.95 -0.99 Å) and included as riding contributions with isotropic displacement parameters 1.2 -1.5 times those of the attached atoms.

Figure 2
Figure 2 Detail of the intermolecular C-H� � �N and C-H� � �O hydrogen bonds, which are shown, respectively, by black and light-blue dashed lines and the C O� � ��(ring) interactions, which are shown by orange dashed lines.Non-interacting hydrogen atoms are omitted for clarity.

Figure 3
Figure 3 Detail of the intermolecular C O� � ��(ring) and C-H� � ��(ring) interactions, shown by orange and green dashed lines, respectively, with noninteracting hydrogen atoms omitted for clarity.

Figure 4
Figure 4Packing viewed along the b-axis direction with intermolecular interactions depicted as in Figs.2 and 3and with non-interacting hydrogen atoms omitted for clarity.

Figure 5
Figure 5The fragment (R = C) used in the database search.

Figure 6 (
Figure 6 (a) The d norm Hirshfeld surface showing the C-H� � �O and C-H� � �N hydrogen bonds to neighboring molecules and (b) the surface calculated over shape function showing the C O� � ��(ring) interaction.

Table 2
Experimental details.
Computer programs: APEX3 and SAINT